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Development and validation of a model for steel grinding media wear in tumbling millsChenje, Tapiwanashe W. January 2007 (has links)
Concern regarding grinding media wear is as old as the invention of the tumbling mill itself. Over the years many techniques have been tried in an attempt to minimize costs associated with grinding. These have included experimentation with different metals, non-metals and different shapes. Through all this, steel grinding balls have proved the most effective media for comminution in tumbling mills. / As old as the tumbling mill is, no accurate technique for estimating the wear of the ball charge has been developed. The mining industry still utilizes the Bond Abrasion test that was developed in the early 1960s. This test which is based solely on the ore properties is inadequate giving a standard deviation in excess of 100%. This can results in high degree of error which for greenfield applications can indicate profitability for non-profitable operations and vice versa. / Peter Radziszewski proposed a decoupled total grinding media wear model that could be used to predict grinding media instead of using the Bond abrasion test. This new model had a standard deviation of 56%, which was a great improvement over the bond abrasion wear estimates. This new model also allowed for the first time, the three wear modes, abrasion, corrosion and impact, responsible for grinding media wear to be quantified. This was an important development as the ability to identify the dominant wear mode in any given operation gives operators a chance to target reduction of wear. The current mining trend is towards exploitation of lower grade ores as the higher grades become depleted. These low-grade ores require finer grinding for the liberation of the value minerals. This in turn means higher ball consumption and higher beneficiation costs. The reduction of ball wear to minimise the overall cost of ore processing operation is going to be a primary concern for all concentrators. / The objective of the research that forms the basis of this thesis was to improve the accuracy of the decoupled grinding media wear model. This was achieved by refining the tests and methodologies used to determine the wear components that make up the decoupled grinding media wear model, performing fundamental testwork to determine a more accurate structure of the decoupled model, and validating this new model. / The new model termed the "modified decoupled grinding media wear model", gives better accuracy in predicting grinding media wear than both the Bond abrasion test and the original decoupled model.
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Development and validation of a model for steel grinding media wear in tumbling millsChenje, Tapiwanashe W. January 2007 (has links)
No description available.
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Identification of an industrial scale semi-autogenous grinding circuit for control purposesGiddy, Mark Robert 29 January 2015 (has links)
Optimisation of the control of an autogenous grinding circuit requires a better
understanding of system dynamics than exists at present. To this end extensive
operating data were acquired on an industrial semi-autogenous milling
circuit and a model was developed to explain the circuit responses to
changes in input variables. This model represents the trends in the data fairly
accurately and showed that:
• When an excess o f slurry was present in Me load (i.e. more than the volume
of the voids) a pool of slurry forms st the toe of the load.
• The complexity of the power dependence on the variables describing the
mill load defied dynamic modelling with toe limited knowledge avail-
• The key parameters determining grinding efficiency vary constantly as
the grinding environment is disturbed indicating a need for adaptive con-
• The flow through the mili is adequately modelled by a single well mixed
Itwasalso clear that maximisation of the power with respect to themass alone
was insufficient, and that control of the feed dilution water rate is essential.
Mill discharge slurry theology was studied eo gain an insight into conditions
in the load. An energy balance using temperature measurements around th t
mill discharge sump provided a very reliable estimate of the mill discharge
density. This estimate was not successfully used for control although this
potential should be exploited. Attempts to commission an on-line measurement
of discharge slurry viscosity failed.
Several theories and ideas were tested in a production environment subject
to a multiplicity of disturbances and conclusive qualitative results were obtained.
An improved understanding of milling circuit dynamics and a rationalisation
of where controi can be improved has resulted from this work.
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Effects of grinding media shapes on ball mill performanceLameck, Niyoshaka Nistlaba Stanley 31 October 2006 (has links)
Student number : 0318567G
School of Chemical and Metallurgical Engineering
Faculty of Engineering / Comminution is an important process in mineral processing, power plants, cement
production and pharmaceutical industries. It is costly and an inefficient process in
terms of energy requirements and steel consumption related to grinding media and
liners.
Spherical grinding media are predominantly used in final stages of ore grinding. The
spherical balls change shape through breakage and wear. Though this is universal in
milling, its contribution and effect on milling kinetics, load behaviour and mill power
is not fully established. One area that is usually ignored is the relationship between
media shape and mill power.
The objective of this dissertation was to investigate how media shape affects
grinding. Ball size distribution inside an industrial mill was analysed in terms of
shapes and sizes. Load behaviour, mill power and breakage as affected by media
shapes were studied in a pilot laboratory mill. An inductive proximity probe, light
emitting diode, phototransistor and video photographs were used to determine the
load orientation in terms of toe and shoulder positions. A load beam was used to
measure the torque exerted by the charge.
The variation in load orientation and mill power with speed among different media
shapes was observed. Higher shoulder positions were noted with cylpebs than with
worn and spherical balls. The power increased to a maximum with increasing mill
speed for all media shapes reaching its peak at different mill speeds for the three
shapes studied.
Variations of breakage rates with media shapes were found; higher breakage rates
were noted with spherical media but the differences narrows with decreasing feed size
and increasing material fractional filling U. Considering that worn balls in an industrial mill charge constitute about 15 to 40
percent and that the highest difference in breakage rate observed being nine percent
for purely one shape charge; it is very doubtful whether it is worthwhile in attempting
to develop techniques for removing worn balls from the mill.
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Abrasão-corrosão em corpos moedores na moagem de minério de ferro. / Abrasion-corrosion of grindin media during the processing of iron ore.Massola, Camila Peres 17 March 2015 (has links)
O desgaste de corpos moedores constitui um custo importante na indústria mineral, que depende da operação de cominuição para promover a liberação das espécies minerais e produzir concentrados. Embora se conheça alguns dos mecanismos individuais que afetam o desgaste, a interação entre eles num sistema tão complexo quanto um moinho ainda precisa ser melhor entendido. Este trabalho avaliou o efeito da corrosão no desgaste de bolas de aço e de ferro fundido branco de alto cromo durante a moagem de minério de ferro, através de ensaios eletroquímicos e de desgaste em moinho de laboratório. Foi feita uma alteração no modo tradicional de realização do ensaio de polarização potenciodinâmica, utilizando polpa de minério de ferro a 70% de sólidos (em peso) como eletrólito. As curvas de polarização obtidas foram compatíveis com os resultados de desgaste, de modo que as curvas correspondentes aos metais na condição mais ativa estavam associadas às menores taxas de desgaste nos ensaios de moagem em laboratório, demonstrando que os ensaios de polarização realizados podem ser utilizados como indicativo do comportamento do metal na moagem de minério de ferro. Sobretudo, os testes demonstraram que o desgaste das bolas de aço é devido, principalmente, à abrasão, já que uma pequena diferença, de apenas 8%, foi observada nas taxas de desgaste nas condições avaliadas (polpa no pH 5 e pH 8). Por outro lado, as bolas de ferro fundido branco de alto cromo, que são mais caras, são mais propensas a resistir ao desgaste em polpa ácida, em que a taxa de desgaste foi 40% menor que a determinada em pH 8. / The wear out of grinding media represents a major cost in the mineral industry, which strongly depends on the mineral liberation to achieve the production of concentrates. Although some of the individual mechanisms that affect wear are already known, the interaction between them in such a complex system as an ore mill still needs further investigation. This work analyzed the effect of corrosion on the wear of balls made of steel and high chromium cast iron, while grinding iron ore, by means of electrochemical tests and wear tests conducted in a laboratory mill. A modification of the traditional potenciodynamic polarization test is proposed, using iron ore slurry at 70% w/w as an electrolyte. The results of the polarization curves were compatible with those from the wear tests, as the curves corresponding to the condition in which the metal showed the more active behavior were associated to the lower wear rates in the wear tests, suggesting that the modified polarization tests can be used as an indicative of the metal alloy behavior while grinding iron ore. Moreover, it demonstrated that the wear of steel balls is mainly due to abrasion, as a slight difference of 8% in their wear rates was observed in both conditions investigated (pH 5 and pH 8). On the other hand, the high chromium cast iron balls, which are more expensive, were more likely to resist wear in slurry at pH 5, achieving a wear rate 40% lower than in pH 8.
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Slurry density influence on ball mill behaviorCarson, Harry Benjamin, 1943- January 1969 (has links)
No description available.
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Modelling and simulation of Brunswick mining grinding circuitDel Villar, René January 1985 (has links)
No description available.
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Abrasão-corrosão em corpos moedores na moagem de minério de ferro. / Abrasion-corrosion of grindin media during the processing of iron ore.Camila Peres Massola 17 March 2015 (has links)
O desgaste de corpos moedores constitui um custo importante na indústria mineral, que depende da operação de cominuição para promover a liberação das espécies minerais e produzir concentrados. Embora se conheça alguns dos mecanismos individuais que afetam o desgaste, a interação entre eles num sistema tão complexo quanto um moinho ainda precisa ser melhor entendido. Este trabalho avaliou o efeito da corrosão no desgaste de bolas de aço e de ferro fundido branco de alto cromo durante a moagem de minério de ferro, através de ensaios eletroquímicos e de desgaste em moinho de laboratório. Foi feita uma alteração no modo tradicional de realização do ensaio de polarização potenciodinâmica, utilizando polpa de minério de ferro a 70% de sólidos (em peso) como eletrólito. As curvas de polarização obtidas foram compatíveis com os resultados de desgaste, de modo que as curvas correspondentes aos metais na condição mais ativa estavam associadas às menores taxas de desgaste nos ensaios de moagem em laboratório, demonstrando que os ensaios de polarização realizados podem ser utilizados como indicativo do comportamento do metal na moagem de minério de ferro. Sobretudo, os testes demonstraram que o desgaste das bolas de aço é devido, principalmente, à abrasão, já que uma pequena diferença, de apenas 8%, foi observada nas taxas de desgaste nas condições avaliadas (polpa no pH 5 e pH 8). Por outro lado, as bolas de ferro fundido branco de alto cromo, que são mais caras, são mais propensas a resistir ao desgaste em polpa ácida, em que a taxa de desgaste foi 40% menor que a determinada em pH 8. / The wear out of grinding media represents a major cost in the mineral industry, which strongly depends on the mineral liberation to achieve the production of concentrates. Although some of the individual mechanisms that affect wear are already known, the interaction between them in such a complex system as an ore mill still needs further investigation. This work analyzed the effect of corrosion on the wear of balls made of steel and high chromium cast iron, while grinding iron ore, by means of electrochemical tests and wear tests conducted in a laboratory mill. A modification of the traditional potenciodynamic polarization test is proposed, using iron ore slurry at 70% w/w as an electrolyte. The results of the polarization curves were compatible with those from the wear tests, as the curves corresponding to the condition in which the metal showed the more active behavior were associated to the lower wear rates in the wear tests, suggesting that the modified polarization tests can be used as an indicative of the metal alloy behavior while grinding iron ore. Moreover, it demonstrated that the wear of steel balls is mainly due to abrasion, as a slight difference of 8% in their wear rates was observed in both conditions investigated (pH 5 and pH 8). On the other hand, the high chromium cast iron balls, which are more expensive, were more likely to resist wear in slurry at pH 5, achieving a wear rate 40% lower than in pH 8.
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Modelling and simulation of Brunswick mining grinding circuitDel Villar, René January 1985 (has links)
No description available.
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